Photographs of the Sandpiper
Imogen's main characteristic is that she is a talented photographer, meaning that she understands how to frame things well. This is explained through the imagery of bird-watching photography, especially her prized work with the Sandpiper. As an image, it represents Imogen's ability to frame nature in a meaningful way. This image is fulfilled when she frames the death of Jim in her psychology.
The imagery of violence
It goes without saying that the novel is gory. It includes graphic depictions of people exploding, or being dismembered or shot to death. The inclusion of this imagery is the center of the novel's meaning. Just as Jim had to see things he wished he didn't, so too the reader must bear witness to it through prose.
The imagery of randomness
The novel depicts the emotional effect of paranoia very well by showing bombs as random explosions. Yes, technically they are projectiles, but the novel chooses to explain them through their phenomenology. To the soldiers in the trenches, the bombs meant that there was always the chance of a random explosion. This causes deep psychological damage, because it means the world is so unpredictable that they never get freed of the fear of violent death.
The imagery of Eden
Jim works as a warden in an estuary where he loves to watch birds. That means that he has the same role as the biblical character of Adam, just a silent guardian over an Edenic garden. When he leaves behind his role, he heads toward his death, just as Adam's departure from paradise implied his own inevitable death. By associating Jim with the patriarch Adam, the effect of his observation is that it's universal. His point of view is eternal and exact. The novel is humanistic in this regard.
The image of the crow migration
In Greek literature, if you notice birds during a battle, you're probably an oracle or a prophet. This is also the case for Jim, who notices that the birds continue on their migration. That means that nature doesn't flinch when we die, and the rest of the universe just keeps going. Perhaps this insight is what leads Jim to his existential enlightenment and his acceptance of his violent death.
